The proposed research is divided into four parts, each of which involves the application of NMR spectroscopy to problems in conformational analysis or structural determination. In the first part, the usefulness of 17 O NMR in dynamic NMR will be examined (N-tert butyl nitramine), and 17 O NMR will be used to assign structures to several bis-trimethylsilyl amides (amide or imidate structure). The ability of 33S NMR to distinguish between singly and doubly bonded sulfur will be determined. Solvents near the critical temperature will be used in some cases to reduce the line widths. Many compounds of biological importance contain oxygen or sulfur, and the spectra will provide information about the potential of 17 O on 33 S NMR for studies of these compounds. In part II, barriers to rotation in several selenium-containing compounds will be measured to show that selenium can be an effective - donor. In part III, hindered rotation and nitrogen inversion in acyl aziridines will be studied by dynamic NMR spectroscopy to obtain information about the importance of conjugation in the amide bond of these compounds, and to demonstrate that pyramidel nitrogen in an amide can still bond effectively with the carbonyl group. Part IV describes a dynamic NMR study of several nonsubstituted cyclodecanes. The relative preferences of the substituents for the various possible positions in the ring will be determined and will provide an experimental check on the literature values for CH 3 obtained by molecular mechanics calculations.